LIVERPOOL, England -- Three quick thoughts on Liverpool's 4-3 Premier League win over Manchester City at Anfield on Sunday.

1. Liverpool destroy Man City's aura of invincibility

Liverpool produced one of the performances of the season to end Manchester City's hopes of an unbeaten Premier League campaign with a stunning 4-3 victory at Anfield on Sunday.

Despite the £142 million sale of Philippe Coutinho to Barcelona a week ago and a hamstring injury that forced £75 million new-boy Virgil van Dijk to watch from the stands, Liverpool were still able to overrun Pep Guardiola's league leaders and record their fifth successive Anfield victory against City.

In what was a tactical masterclass by Liverpool manager Jurgen Klopp, the home side out-ran and out-thought City, pressing Guardiola's men high up the pitch.

Despite the defeat, City remain 15 points clear of second-place Manchester United, who can cut the deficit to 12 points with a victory at home to Stoke City on Monday.

Alex Oxlade-Chamberlain, playing in central midfield, gave Liverpool an early lead with a 20-yard strike on nine minutes, but Leroy Sane hauled City level on 41 minutes by beating goalkeeper Loris Karius at the near post. But just as City appeared to be gaining the upper hand early in the second half, Liverpool regained the lead on 59 minutes when Roberto Firmino scored after forcing John Stones into a mistake on the edge of the penalty area.

Another mistake, this time by Nicolas Otamendi, led to Sadio Mane making it 3-1 with a long-range effort two minutes later. With City's unbeaten run on the brink of ending, Mohamed Salah made it 4-1 after scoring from 35 yards following a poor clearance by goalkeeper Ederson.

Substitute Bernardo Silva gave City hope of a late fightback by making it 4-2 on 83 minutes before Ilkay Gundogan scored another in stoppage time. But Liverpool survived a nervous final three minutes to claim a huge victory, both for themselves and the Premier League.

2. How to stop City: Run at their defenders

Manchester City were not just beaten at Anfield, they were torn apart by Liverpool, who gave further evidence that Guardiola's team can be tested if you target their defenders.

Crystal Palace were the first to expose the weakness in City's armour on New Year's Eve, when Wilfried Zaha tormented their backline all afternoon in a 0-0 draw at Selhurst Park. Bristol City then adopted the same attack-first tactic during the first leg of the Carabao Cup semifinal at the Etihad on Tuesday before losing 2-1 to a late Sergio Aguero goal.

Liverpool ended Manchester City's Premier League unbeaten run with an enthralling 4-3 win at Anfield on Sunday.

Against both Palace and Bristol City, City's defenders were forced to deal with forwards and midfielders prepared to run directly at them and it led to mistakes in both games by the likes of Stones, Danilo and Eliaquim Mangala.

Liverpool's forwards are of much greater quality than anything City have faced so far this season, though, and it showed at Anfield. Salah, Firmino and Mane had the City defence tied up in knots at times and mistakes by Stones, Otamendi and Ederson led directly to three of the home side's four goals.

Stones, in particular, has shown a vulnerability when tested in recent games. He was outmuscled by Firmino for a goal in this game and was also caught out in the win against Bristol City by forwards prepared to run at him.

In previous games, City's forwards have made up for any defensive lapses by scoring goals almost at will to win games. But the defensive frailties were there for all to see at Anfield and they will now be targeted by other teams, both at home and in Europe for the rest of the season.

3. Klopp must stop gambling on goalkeepers

They got away with it in the end, but one of the big problems with Liverpool is that, from one week to the next, there is no certainty as to who will start in goal for Jurgen Klopp's team. Since Christmas alone, Belgium international Simon Mignolet has started two games and Karius three, with the German keeper winning the nod from Klopp for this game after playing in the 2-1 FA Cup third-round victory against Everton last week.

Uncertainty in goal leads to problems in the defence in terms of communication and understanding, but Klopp appeared to have identified that by admitting prior to this game that Karius would become his No. 1 if he grabbed his chance. But by half-time, Karius had made a mistake with the first shot he had to save by allowing Sane's 41st-minute shot to beat him at the near post.

It was a well-struck shot by Sane, but it went in not because of the power, but because Karius's positioning was all wrong. The question is whether that is because he has not played often enough to be sure of his angles or whether, more bluntly, he simply isn't good enough at this level.

Mignolet's erratic performance during last month's 3-3 draw at Arsenal suggested he was not good enough and now Karius, a £4.7 million buy from Mainz in 2016, has given further evidence of his shortcomings.

Liverpool are now sitting on a huge transfer kitty following the sale of Coutinho to Barcelona, so reinvesting that in a keeper like Kasper Schmeichel, Jack Butland or Jan Oblak would surely be sensible decision.

On this occasion, Liverpool's forwards spared the goalkeeper's blushes with their rampant display, but Klopp cannot rely on that forever.

Mark Ogden is a senior football writer for ESPN FC. Follow him @MarkOgden_